Work sucking device

ABSTRACT

A workpiece sucking device comprises a buffering mechanism for absorbing shock generated when a workpiece is engaged/disengaged. The buffering mechanism includes a linear rail member which is fixed to a body and a slider which makes sliding movement along the rail member. A workpiece is prevented from rotating by an engagement of the slider with the rail member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a workpiece sucking device forattracting and transporting a workpiece by using a suction memberoperated by a fluid sucking action under negative pressure.

2. Description of the Related Art

A suction device has hitherto been used which is installed with asuction pad as a means for attracting and transporting a workpiece. Thesuction device is provided with a buffering mechanism which functions asabsorbing the shock generated when the workpiece is attracted by meansof the suction pad or when the workpiece is disengaged from the suctionpad.

Further, the suction device is provided with a rotation-preventivemechanism for preventing the workpiece from rotating when the workpieceattracted by the suction pad is transported.

In the above suction device, the buffering mechanism and therotation-preventive mechanism are constructed as separate membersrespectively.

However, the above suction device has an inconvenience in that it cannotbe miniaturized since the buffering mechanism and therotation-preventive mechanism are separately provided respectively.

Furthermore, when a resin material is used for the suction device, atemperature condition limits an environment where the workpiece suctiondevice can be installed. For example, it is difficult to use the suctiondevice in an environment where the suction device is installed at a hightemperature (for example, not less than 100° C.) or at a low temperature(for example, not more than 0° C.).

An object of the present invention is to provide a workpiece suckingdevice which can be miniaturized and which can be widely used inaccordance with the temperature condition in the environment where theworkpiece sucking device is installed.

SUMMARY OF THE INVENTION

A buffering mechanism according to the present invention functions aspreventing the workpiece from rotating as well as absorbing the shockgenerated when a workpiece is engaged/disengaged, therefore allowing theworkpiece sucking device to be miniaturized. Further, all ofconstitutive components including a retainer except for a suction memberare made of metal materials. Accordingly, the workpiece sucking devicecan be widely used in accordance with a temperature condition in anenvironment where the workpiece sucking device is installed.

Preferably, a suction pad functioning as the suction member is formed ofconductive fluorine-based rubber composed of vulcanized fluorine-basedrubber and carbon black.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front view illustrating a workpiece sucking deviceaccording to an embodiment of the present invention;

FIG. 2 illustrates the operation depicting a state in which a slider anda connecting member are displaced along a rail member from the initialpositions shown in FIG. 1;

FIG. 3 shows, with partial cutaway, a perspective view illustrating therail member and the slider which constitute a buffering mechanism; and

FIG. 4 shows a vertical sectional view illustrating a suction pad whichconstitutes the workpiece sucking device shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, reference numeral 10 indicates a workpiece sucking deviceaccording to an embodiment of the present invention.

The workpiece sucking device 10 comprises a body 12 which is formed witha hole (not shown) penetrating therethrough in the axial direction, asuction pad (suction member) 16 which is installed to the lower end ofthe body 12 by the aid of a connector 14, and a joint member 18 which isconnected to the-upper end of the body 12 and which is formed with aport (not shown) communicating with the hole.

The body 12 has a buffering mechanism 22 provided at a side portionthereof. The buffering mechanism 22 absorbs the shock generated when aworkpiece 20 (see FIG. 2) is engaged/disengaged and prevents theworkpiece 20 from rotating while it is transported. All of constitutivecomponents except for the suction pad 16 are made of metal materials.

The suction pad 16 is formed of, for example, conductive fluorine-basedrubber. As shown in FIG. 4, the suction pad 16 includes a thin-walledskirt section 24 contacting with the workpiece 20, and a connectingsection 28 formed integrally with the skirt section 24 and having a hole26 connected to the connector 14.

The body 12 has a cylindrical member 30. The cylindrical member 30 hasan unillustrated through-hole formed at the inside thereof. Thethrough-hole is a passage for allowing a fluid under negative pressureto flow therethrough. A stopper section 32 protruding outwardly by apredetermined dimension is formed at the end of the cylindrical member30.

As shown in FIG. 3, the buffering mechanism 22 includes a rail member34.which is fixed to the side of the body 12 by the aid of unillustratedscrew members to be inserted into attachment holes 33, a slider (slidemember) 36 which is provided linearly displaceably along the rail member34 in accordance with the guiding action of the rail member 34, and aconnecting member 38 which is fixed to the slider 36 by the aid ofunillustrated screw members to be inserted into attachment holes 37 andwhich is displaceable integrally with the slider 36.

As shown in FIG. 3, a plurality of balls 42 and a retainer 46 aredisposed between the rail member 34 and the slider 36. The plurality ofballs 42 roll along rolling grooves 40 formed at the sides of the railmember 34. The retainer 46 rollably retains the balls 42 in circularholes 44. The retainer 46 is secured to the slider 36 and isdisplaceable integrally with the slider 36. All parts of the bufferingmechanism 22 including the retainer 46 are made of metal materials.

A stopper plate 47 preventing the slider 36 from disengaging from therail member 34 is connected to the end of the rail member 34 by the aidof a screw member 49. A cover member 51 fastening the retainer 46 isconnected to the end of the slider 36 by the aid of screw members 53.

In this arrangement, it is preferable that lubricating oil, which doesnot generate dust so much and which can be used in a wide temperaturerange (for example, a range from −40° C. to 200° C.), is applied, forexample, to the sliding surfaces of the rolling grooves 40 and the balls42 retained by the retainer 46 and to the sliding surfaces of the railmember 34 and the slider 36.

As shown in FIG. 2, the connecting member 38 is formed with a pair ofattachment holes 48 a, 48 b which are separated from each other by apredetermined distance. The workpiece sucking device 10 can be fixed toan unillustrated robot arm 56 by the aid of fastening members 55 screwedinto the attachment holes 48 a, 48 b from the side of the arm 56 asdescribed later on.

The connecting member 38 has a projection 50 formed at the end thereof.The projection 50 abuts against the stopper section 32 which is providedfor the body 12 to restrict the displacement of the connecting member38. A spring 52 is fastened between the projection 50 and the railmember 34. The projection 50 is urged in a direction of separating fromthe first end of the rail member 34 in accordance with the action of theresilient force of the spring 52. That is, the projection 50 is urged sothat it abuts against the stopper section 32. The shock generated whenthe workpiece 20 is engaged/disengaged is absorbed by the aid of theresilient force of the spring 52. The first end of the spring 52 isfastened to the rail member 34, and the second end of the spring 52 isfastened to the projection 50.

The joint member 18 is composed of a so-called one-touch joint, and itis connected to an unillustrated negative pressure supply source via atube 54 which is inserted into the port. The fluid under negativepressure which is supplied from the negative pressure supply source isintroduced into the suction pad 16 via the unillustrated through-hole ofthe body 12.

The workpiece sucking device 10 according to the embodiment of thepresent invention is basically constructed as described above. Next, itsoperation, function, and effect will be explained. The followingdescription will be made assuming that the state shown in FIG. 1 residesin the initial position.

At first, the rail member 34 is connected to the side of the body 12 byscrewing the unillustrated screw members into the attachment holes 33formed for the rail member 34. Subsequently, the unillustrated screwmembers are screwed into the attachment holes 37 formed for the slider36 to fix the connecting member 38 to the slider 36. Further, thefastening members 55 are screwed into the attachment holes 48 a, 48 bformed for the connecting member 38 to fix the workpiece sucking device10, for example, to the first end of the robot arm 56.

The workpiece sucking device 10 is then moved downwardly in accordancewith the displacement action of the robot arm 56 to attract theworkpiece 20 by the aid of the suction pad 16. During this process, asshown in FIG. 2, the connecting member 38 and the slider 36 areintegrally moved downwardly along the rail member 34 against theresilient force of the spring 52. The projection 50 of the connectingmember 38 is separated from the stopper section 32. Accordingly, theshock generated in attracting the workpiece 20 can be absorbed by theresilient force of the spring 52.

After the workpiece 20 is attracted by using the suction pad 16 which isoperated by a fluid sucking action under negative pressure, the robotarm 56 is displaced, and the workpiece sucking device 10 is movedupwardly to a predetermined position. Accordingly, the initial positionis restored where the projection 50 abuts against the stopper section 32in accordance with the resilient force of the spring 52 (see FIG. 1).

After attracting the workpiece 20, the robot arm 56 is rotated in apredetermined direction. The rotary action of the robot arm 56 isstopped at a predetermined position. Further, the workpiece suckingdevice 10 is moved downwardly in accordance with the displacement actionof the robot arm 56. Accordingly, the workpiece 20 can be transportedand positioned at a predetermined position.

The transported workpiece 20 is prevented from rotating by theengagement between the rail member 34 and the slider 36. That is, therail member 34 and the slider 36 as the guide means simultaneouslypossess the function of preventing the workpiece 20 attracted by thesuction pad 16 from rotating so that the workpiece 20 may not bedisengaged from the suction pad 16. Accordingly, it is possible tostably transport the workpiece 20.

In other words, the slider 36 is provided displaceably only in the axialdirection of the rail member 34 in accordance with the balls 42 rollingalong the rolling grooves 40. The slider 36 is provided not to makerotation about the axial center of the rail member 34. Accordingly, thefunction of preventing the slider 36 from rotating is achieved.

Since the slider 36 is smoothly displaced linearly along the rail member34 in accordance with the rolling action of the balls 42, no backlash isgenerated even if the workpiece sucking device 10 is used for a longperiod. Accordingly, the transported position of the workpiece 20 can bedetermined highly accurately.

Further, all of the constitutive components except for the suction pad16 are formed of the metal materials. Accordingly, the,workpiece suckingdevice 10 can be widely used in accordance with the temperaturecondition in the environment where the workpiece sucking device 10 isinstalled.

For example, when the workpiece 20 is an IC chip, it is necessary forthe suction pad 16 to be formed of a conductive material for thefollowing reason. That is, if the suction pad 16 is formed of anon-conductive material, the current of the charged IC chip flows out ofthe IC chip, therefore resulting in destroying the IC chip.

Furthermore, since the energized IC chip is at a relatively hightemperature, it is necessary for the suction pad 16 to resist the heatof the IC chip.

As a conductor excellent in resisting the heat, conductive siliconerubber composed of silicone rubber and carbon black can be used. Theconductive silicone rubber has been widely used as a material for asuction pad. However, since the conductive silicone rubber is inferiorin durability, a problem arises that the conductive silicone rubber usedfor the suction pad cannot be durable for repeatedly attracting andtransporting the workpiece.

The suction pad 16 of the workpiece sucking device 10 according to theembodiment of the present invention is composed of conductivefluorine-based rubber. The conductive fluorine-based rubber is acomposite material composed of vulcanized fluorine-based rubber andcarbon black.

The strength and the heat resistance of the fluorine-base rubber aregreatly improved by means of vulcanization. That is, the vulcanizedfluorine-based rubber makes excellent the strength, the durability, andthe heat resistance for the conductive fluorine-based rubber. However,it is impossible to sufficiently obtain the durability and the heatresistance in the suction pad produced by using non-vulcanizedfluorine-based rubber.

Carbon black itself is an excellent conductor, therefore being acomponent which brings about the conductivity for the conductivefluorine-based rubber.

The ratio between the fluorine-based rubber and carbon black is set suchthat the suction pad 16 has the heat resistance, the durability, and theelectric conductivity as desired.

The suction pad 16 incorporated in the workpiece sucking device 10according to the embodiment of the present invention can be produced asfollows.

At first, the fluorine-based rubber, a vulcanizing agent for thefluorine-based rubber, and carbon black are uniformly mixed at apredetermined ratio to prepare a mixture.

Subsequently, the mixture is heated and maintained at about 180° C. forabout 10 minutes (primary vulcanization). Further, after the temperatureof the mixture is raised stepwise to about 230° C., it is maintained andheated for about 24 hours (secondary vulcanization). During the heatingprocesses, the fluorine-based rubber is vulcanized by the vulcanizingagent. Furthermore, the vulcanized fluorine-based rubber and carbonblack are formed in a composite way. The conductive fluorine-basedrubber is thus obtained. As described above, the stepwise processes ofincreasing and constantly maintaining the temperature of the mixture areperformed. Accordingly, it is possible to avoid cracks which would beotherwise caused by expanded gas components that are generated invulcanizing the conductive fluorine-based rubber.

Finally, the suction pad 16 is produced by shaping the conductivefluorine-based rubber according to a known shaping method.

The suction pad 16 produced as described above is excellent in the heatresistance, the electric conductivity and the durability. Therefore, theIC chip is not harmfully influenced even when it is repeatedly attractedand transported at the high temperature for a long period. Accordingly,the durability of the suction pad 16 can be improved to a greaterextent.

The buffering mechanism according to the present invention functions aspreventing the workpiece from rotating as well as absorbing the shockgenerated when the workpiece is engaged/disengaged. Accordingly, theworkpiece sucking device can be miniaturized since it is unnecessary toprovide respective members separately.

In the present invention, all of the constitutive components except forthe suction pad to function as the suction member are formed of themetal materials. Accordingly, the workpiece sucking device can be widelyused in accordance with a temperature condition in an environment wherethe workpiece sucking device is installed.

What is claimed is:
 1. A workpiece sucking device for attracting andtransporting a workpiece by means of a suction member operated by afluid sucking action under a negative pressure, said device comprising:a body for supporting said suction member; and a buffering mechanismprovided at a side portion of said body, for absorbing shock generatedwhen said workpiece is engaged/disengaged, wherein: said bufferingmechanism includes a linear rail member which is fixed to an externalsurface of said body in an axial direction of said body and a slidemember which is slidably displaceable along said rail member, and saidworkpiece is prevented from rotating by means of an engagement of saidslide member with said rail member, wherein said buffing mechanismincludes a connecting member which is displaceable integrally with saidslide member, and a spring member which is installed between aprojection of said connecting member and an end of said rail member. 2.The workpiece sucking device according to claim 1, wherein a pluralityof balls for making rolling movement along a rolling groove of said railmember and a retainer formed with holes for rollably holding said ballsare provided between said rail member and said slide member, and allconstitutive components of said workpiece sucking device including saidretainer except for said suction member are formed of metal materials.3. The workpiece sucking device according to claim 1, wherein allconstitutive components of said workpiece sucking device except for saidsuction member are formed of metal materials.
 4. The workpiece suckingdevice according to claim 1, wherein said suction member is composed ofa suction pad, and said suction pad is formed of conductivefluorine-based rubber composed of vulcanized fluorine-based rubber andcarbon black.
 5. The workpiece sucking device according to claim 1,wherein a stopper section, which makes abutment against a projection ofsaid slide member to regulate displacement of said slide member, isprovided at one end of said body in said axial direction.
 6. Theworkpiece sucking device according to claim 1, wherein said body iscomposed of a cylindrical member formed with a hole penetrating in saidaxial direction, a joint member for being connected to a tube isconnected to a first end of said cylindrical member in said axialdirection, and said suction member is coaxially connected via aconnector to a second end of said cylindrical member in said axialdirection.